I like the small size (34cm); the cushion is brought out quickly and is well suited for small training sessions in between. Just as quickly it is stowed again.
What is very important for me also: The material feels comfortable and is odorless.
The knobs are on both sides at different heights; I prefer especially with exercises while standing the taller stems, because I feel as pleasant circulation stimulating. I was able to improve my sense of balance in any case.
Somewhat disappointed (and surprised) I was (inflate as air or cleaning) on the absence of both a tutorial and a care instructions. A small brochure with the most important information in this respect would have been useful.
Good exercises specifically for this pillow I luckily found on YouTube. (URL I can not specify here; just look at coordinating training and balance training with Sissel Balance Fit)
I find this pillow recommended, but would wish they came with a small manual in the future.